Light emitting diode (LED) is a solid-state light emitting element formed of a semiconductor material normally composed of III-V group chemical elements such as gallium phosphide, gallium arsenide, or gallium nitride. When a voltage is applied to the compound semiconductor, electrode voltage will make a large amount of electron holes and a large amount of electrons meet together to form electron-hole recombination on the light emitting layer. Meanwhile, the electrons will degenerate to a lower energy level and will be released in the form of photons. Thus, electrical energy is converted into optical energy and emits a light.
In order to increase the luminance of light output, the LED further includes a reflective structure for reflecting the light generated by the light emitting layer to an ideal direction of light output. Conventional reflective structure is a silver mirror which may go through phase change when the silver mirror is affected by temperature during the manufacturing process. When the silver mirror changes to liquid state, the silver may diffuse to the peripheral. Therefore, the edge of silver mirror cannot be aligned with the edge of other layer of the LED, and must be slightly indented and covered with a barrier layer normally formed of titanium tungsten.
In a conventional LED, the silver mirror and the barrier material are stacked together to from a reflective element; therefore the manufacturing process becomes very complicated. Moreover, the stability of the silver mirror is an issue that needs to be considered. Therefore, there are many issues that can be improved.